| Time：1141008 (Wed.) 14:20~16:20 Speaker：Prof.陳劭宇/ Chen, Shao-Yu 國立臺灣大學凝態科學研究中心/Center for Vondensed Matter Sciences, National Taiwan University Title：Dark Excitons in 2D Materials Abstract： The tightly bound excitons in two-dimensional (2D) materials have attracted significant interest due to their remarkable optical, spintronic, and valleytronic properties. Although brightly luminescent excitons, which directly couple with light, have been extensively studied for their effective light-matter interactions, dark excitons are much less well understood. Nonetheless, dark excitons display unique physical properties, such as longer population lifetimes and greater diffusion lengths, which are essential for manipulating exciton dynamics in practical devices. Understanding and controlling both bright and dark excitons is crucial for exploring many-body Coulomb interactions and advancing exciton-based applications with new functionalities. In my talk, I will examine the many-body interactions of dark excitons in 2D transition metal dichalcogenides using optical spectroscopy. Our research has identified dark-exciton-mediated biexcitons and exciton-trions in high-quality monolayer WSe2 devices, revealing significant interactions between bright and dark excitons and highlighting the crucial role of dark excitons in these systems. Additionally, we have found that dark excitons can facilitate efficient light upconversion through exciton-exciton annihilation. This discovery opens new possibilities for manipulating dark excitons and potentially improves their use in nanophotonic 2D-material-based photovoltaic and photocatalytic applications. Place：S101, Gongguan Campus, NTNU |
